Fluoroelastomer composition for crosslinking

ABSTRACT

An elastomer composition for crosslinking which comprises (A) a compound having at least two crosslinkable reactive groups represented by the formula (I): 
                 
 
wherein R 1  are the same or different and each is fluorine atom or a monovalent organic group, and (B) an elastomer having a curing site capable of reacting with the crosslinkable reactive group (I). The composition provides a crosslinked article which possesses improved mechanical strength and heat resistance and has excellent chemical resistance.

TECHNICAL FIELD

The present invention relates to an elastomer composition forcrosslinking which can provide a crosslinked rubber molded articlehaving good sealing property and excellent mechanical strength and heatresistance at high temperatures, and particularly relates to afluorine-containing elastomer composition for crosslinking.

BACKGROUND ART

Fluorine-containing elastomers, particularly perfluoro elastomers mainlycomprising a tetrafluoroethylene (TFE) unit are widely used as a sealingmaterial used under hard environment because of excellent chemicalresistance, solvent resistance and heat resistance thereof.

However requirements for characteristics have become rigorous with theadvance of technology. In the fields of aeronautics, space,semi-conductor production apparatuses and chemical plants, a sealingproperty under high temperature environment of 300° C. or more isdemanded.

To cope with such requirements, proposals have been made to enhance heatresistance by improving a crosslinking system, and there are knowncrosslinking systems, for example, a triazine crosslinking system forforming a triazine ring with an organotin compound by using afluorine-containing elastomer having a nitrile group introduced as acrosslinking point (for example, JP-A-58-152041), an oxazol crosslinkingsystem for forming an oxazol ring with bisaminophenol similarly by usinga fluorine-containing elastomer having a nitrile group introduced as acrosslinking point (for example, JP-A-59-109546), an imidazolecrosslinking system for forming an imidazole ring with a tetraminecompound (for example, JP-A-59-109546) and a thiazole crosslinkingsystem for forming a thiazole ring with bisaminothiophenol (for example,JP-A-8-104789).

Among those crosslinking systems, when crosslinking a nitrilegroup-containing perfluoro elastomer with a tetramine compound, heatresistance of the obtained crosslinked rubber molded article is enhancedas compared with conventional crosslinking systems, but the moldedarticle is deteriorated remarkably at high temperature exceeding 300° C.as compared with the triazine crosslinking and oxazole crosslinkingsystems.

On the other hand in the triazine crosslinking and oxazole crosslinkingsystems, the molded article is deteriorated significantly against aminesand high temperature steam, and therefore application thereof islimited.

An object of the present invention is to provide an elastomercomposition for crosslinking which can give a crosslinked rubber moldedarticle possessing particularly improved mechanical strength and heatresistance at high temperatures and having excellent chemicalresistance.

Another object of the present invention is to provide a novelcrosslinking agent.

DISCLOSURE OF INVENTION

Namely the present invention relates to an elastomer composition forcrosslinking which comprises (A) a compound having at least twocrosslinkable reactive groups represented by the formula (I):

wherein R¹ are the same or different and each is fluorine atom or amonovalent organic group, and (B) an elastomer having a curing sitecapable of reacting with the crosslinkable reactive group (I).

The compound (A) is a novel crosslinking agent since its action as acrosslinking agent has not been known.

Example of the compound (A) is preferably a compound represented by theformula (II):

wherein R¹ are as defined above, R² is —SO₂—, —O—, —CO—, an alkylenegroup which may have been substituted,

or a single bond.

Example of the elastomer (B) which can be used preferably is afluorine-containing elastomer, particularly a perfluoro elastomer havinga nitrile group, a carboxyl group and/or an alkoxycarbonyl group as acuring site.

Among the above-mentioned compounds (A), the compound represented by theformula (III):

wherein R³ is an alkyl group which has 1 to 6 carbon atoms and may havebeen substituted, is a novel compound which is an object of the presentinvention.

The present invention also relates to a crosslinked rubber moldedarticle obtained by crosslinking the elastomer composition forcrosslinking of the present invention.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a chart of infrared spectroscopic analysis of afluorine-containing elastomer A having a CN group which was obtained inPreparation Example 1.

BEST MODE FOR CARRYING OUT THE INVENTION

When the elastomer composition for crosslinking of the present inventionis crosslinked, its crosslinking system is analogous to an imidazolecrosslinking system. Namely, in conventional imidazole crosslinking, forexample, a crosslinking structure:

is formed, but in the present invention, as represented by:

there is a N—R¹ bond instead of a N—H bond of the imidazole ring. It canbe considered that this N—R¹ bond greatly contributes to enhancement ofheat resistance. Therefore in the present invention, the compound (A)acting as a crosslinking agent is an important factor. The compound (A)is explained hereinbelow.

The compound (A) has at least two crosslinkable reactive groupsrepresented by the formula (I), preferably two or three groups,particularly preferably two groups in order to form the crosslinkingstructure.

In the crosslinkable reactive group (I), the substituent R¹ is amonovalent organic group other than hydrogen or fluorine atom, andparticularly preferred is a substituent forming the N—R¹ bond having ahigher anti-oxidizing property than the N—H bond. The “substituentforming the N—R¹ bond having a higher anti-oxidizing property than theN—H bond” means a substituent forming the N—R¹ bond which is present ina compound hardly oxidized as compared with a compound having the N—Hbond when the compound (A) forms an imidazole ring.

R¹ is not limited particularly, and examples thereof are an aliphatichydrocarbon group which may have been substituted or a benzyl group orphenyl group which may have been substituted.

At least one of R¹ is, for instance, a lower alkyl group having 1 to 10carbon atoms, particularly 1 to 6 carbon atoms such as —CH₃, —C₂H₅ or—C₃H₇; a fluorine atom-containing lower alkyl group having 1 to 10carbon atoms, particularly 1 to 6 carbon atoms such as —CF₃, —C₂F₅,—CH₂F —CH₂CF₃ or —CH₂C₂F₅; a phenyl group; a benzyl group; a benzylgroup or phenyl group in which 1 to 5 hydrogen atoms have beensubstituted by fluorine atoms such as —C₆F₅ or —CH₂C₆F₅; a benzyl groupor phenyl group in which 1 to 5 hydrogen atoms have been substituted by—CF₃ such as —C₆H_(5-n)(CF₃)_(n) or —CH₂C₆H_(5-n)(CF₃)_(n), wherein n isan integer of from 1 to 5; or the like.

Among them, a phenyl group and —CH₃ are preferred from the viewpoint ofparticularly excellent heat resistance, good crosslinkability andrelatively easy synthesis.

Preferred compound (A) is a compound having at least two crosslinkablereactive groups (I) and represented by the formula (II):

from the viewpoint of easy synthesis. In the formula, R¹ is as definedabove. In the right and left crosslinkable reactive groups (I), thepositions of NH₂ and NHR¹ to the phenyl group may be the same orreverse.

In the compound represented by the formula (II), R² is —SO₂—, —O—, —CO—,an alkylene group which may have been substituted,

or a single bond.

Non-restricted examples of the preferable alkylene group R² which mayhave been substituted are, for instance, a non-substituted alkylenegroup having 1 to 6 carbon atoms or a perfluoro alkylene group having 1to 10 carbon atoms. Examples of the perfluoro alkylene group are:

and the like. Those R² are known as examples of bisdiaminophenylcompounds described in JP-B-2-59177, JP-A-8-120146, etc.

R² may be bonded to any positions of the right and left benzene ringsbut it is preferable that R² is bonded so that either of NH₂ group orNHR¹ group is located at para-position with respect to R² from theviewpoint of easy synthesis and easy crosslinking reaction.

Example of the preferable compound (A) is the compound represented bythe formula (IV):

wherein R⁴ are the same or different and each is an alkyl group having 1to 10 carbon atoms, an alkyl group having fluorine atom and 1 to 10carbon atoms, a phenyl group, a benzyl group, or a phenyl group orbenzyl group in which 1 to 5 hydrogen atoms have been substituted byfluorine atom or —CF₃.

Non-restricted examples of the compound are, for instance,2,2-bis-[3-amino-4-(N-methylamino)phenyl]hexafluoropropane,2,2-bis-[3-amino-4-(N-ethylamino)phenyl]hexafluoropropane,2,2-bis-[3-amino-4-(N-propylamino)phenyl]hexafluoropropane,2,2-bis-[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane,2,2-bis-[3-amino-4-(N-perfluorophenylamino)phenyl]hexafluoropropane,2,2-bis-[3-amino-4-(N-benzylamino)phenyl]hexafluoropropane, and thelike.

The compound (A) explained above is a novel crosslinking agent, hasexcellent mechanical strength, heat resistance and chemical resistanceand provides a crosslinked product having a particularly well-balancedheat resistance and chemical resistance.

Further among the compounds (A), the compound represented by the formula(III):

wherein R³ is an alkyl group which has 1 to 6 carbon atoms and may havebeen substituted, is a novel compound.

In Journal of Polymer Science, edited by Polymer Chemistry, Vol. 20, pg.2381 to 2393 (1982),2,2-bis-[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane issynthesized as a monomer.

Then the crosslinkable elastomer as the component (B) is explainedbelow.

The crosslinkable elastomer (3) may be an elastomer which has a curingsite capable of reacting with the crosslinkable reactive group (I) andis excellent in heat resistance. Examples thereof are, for instance,fluorine-containing elastomers.

Examples of the curing site capable of reacting with the crosslinkablereactive group (I) are a nitrile group (—CN group), carboxyl group(—COOH group) and alkoxycarbonyl group (—COOR group, R is an alkyl grouphaving 1 to 3 carbon atoms).

Examples of the preferable fluorine-containing elastomer arecrosslinkable fluorine-containing elastomers which have a carboxylgroup, nitrile group and/or alkoxycarbonyl group as a curing site on anend of a trunk chain and/or a branched chain and are represented by theformula (V):X¹—[A—(Y)_(p)]_(q)—X²  (V)or the formula (VI):X¹—[A—(Y¹)_(p)]_(q)—[B—(Y²)_(r)]_(s)—X²  (VI)wherein X¹ and X² are the same or different and each is a carboxylgroup, alkoxycarbonyl group, nitrile group, iodine atom, bromine atom orsulfonic acid group, Y, Y¹ and Y² are the same or different and each isa divalent organic group having a carboxyl group, alkoxycarbonyl groupor nitrile group on its side chain, A is an elastomericfluorine-containing polymer chain segment (hereinafter referred to as“elastomeric segment A”), B is a non-elastomeric fluorine-containingpolymer chain segment (hereinafter referred to as “anon-elastomericsegment B”), p is 0 or an integer of from 1 to 10, q is an integer offrom 1 to 5, r is 0 or an integer of from 1 to 10, s is an integer offrom 1 to 3, any one of X¹, X², Y, Y¹ and Y² is a carboxyl group or analkoxycarbonyl group and Y, Y¹ and Y² may be contained at random in thesegment A or B.

The elastomeric segment A may be, for example, perfluoro elastomersegments such as a copolymer rubber represented by the formula (1):

wherein m/n is 95 to 50/5 to 50 (in mole ratio), R_(f) is afluoropolyoxyalkyl group having 1 to 20 carbon atoms or a perfluoroalkylgroup having 1 to 8 carbon atoms anda terpolymer rubber represented by the formula (2):

wherein l/m/n is 95 to 35/0 to 30/5 to 35 (in mole ratio), R_(f) is afluoropolyoxyalkyl group having 1 to 20 carbon atoms or a perfluoroalkylgroup having 1 to 8 carbon atoms, ornon-perfluoro elastomer segments such as a copolymer rubber representedby the formula (3):

wherein m/n is 85 to 60/15 to 40 (in mole ratio), a terpolymer rubberrepresented by the formula (4):

wherein l/m/n is 85 to 20/0 to 40/15 to 40 (in mole ratio), a terpolymerrubber represented by the formula (5):

wherein l/m/n is 95 to 45/0 to 10/5 to 45 (in mole ratio), Z¹, Z² and Z³are fluorine atom or hydrogen atom independently, R_(f) is afluoropolyoxyalkyl group having 1 to 20 carbon atoms or a perfluoroalkylgroup having 1 to 8 carbon atoms,

-   -   (l/m/n is 1 to 80/0 to 80/10 to 50 (in mole ratio), R_(f) is as        defined above).

Examples of Y, Y¹ and Y² for introducing a curing site in the branchedchain are, for instance, iodine-containing monomers represented byCX₂═CX—R_(f) ¹CHRI, wherein X is H, F or CH₃, R_(f) ¹ is a linear orbranched fluoro or perfluoro alkylene group, fluoro or perfluorooxyalkylene group, fluoro polyoxyalkylene group or perfluoropolyoxyalkylene group which may have one or more ether type oxygenatoms, R is H or CH₃, bromine-containing monomers, nitrilegroup-containing monomers represented by:

wherein m is from 0 to 5, n is from 1 to 8,

wherein n is from 1 to 4,

wherein n is from 2 to 5,

wherein n is from 1 to 6,

wherein n is from 1 to 5, in which X³ is CN, COOH or COOR⁵, in which R⁵is a C1 to C10 alkyl group which may have fluorine atom, carboxylgroup-containing monomers, alkoxycarbonyl group-containing monomers, andthe like. Usually iodine-containing monomers, nitrile group-containingmonomers and carboxyl group-containing monomers are suitable.

From the viewpoint of copolymerizability, examples of the suitableiodine-containing monomer are perfluoro(vinyl ether) compounds, forinstance, perfluoro(6,6-dihydro-6-iodo-3-oxa-1-hexene),perfluoro(5-iodo-3-oxa-1-pentene), and the like.

In addition, there are fluoro vinyl ethers described in JP-B-5-63482 andrepresented by the formula:ICH₂CF₂CF₂(OCFY³CF₂)_(n)—OCF═CF₂wherein Y³ is a trifluoromethyl group, n is from 0 to 2.

Also CF₂═CHI, and the like can be used suitably.

When at least one of the end groups X¹ and X² is carboxyl group oralkoxycarbonyl group, a unit having nitrile group or carboxyl group ispreferable from the viewpoint of crosslinkability.

The non-elastomeric segment B is not limited basically as far as thesegment contains fluorine atom and does not have the above-mentionedelastomeric property. The non-elastomeric segment B may be selecteddepending on properties and functions intended to obtain by blockcopolymerization thereof. Particularly a crystalline polymer chainsegment having a crystalline melting point of not less than 150° C. ispreferred in order to impart mechanical properties.

Among the monomers capable of constituting the non-elastomeric segmentB, examples of the fluorine-containing monomer are, for instance, one ormore of perhalo olefins such as TFE, chlorotrifluoroethylene (CTFE),perfluoro(alkyl vinyl ether) (PAVE), hexafluoropropylene (HFP),CF₂═CF(CF₂)_(p)X, wherein p is an integer of from 1 to 10, X is F or Cland perfluoro-2-butene; and partly fluorinated olefins such asvinylidene fluoride, vinyl fluoride, trifluoroethylene,CH₂═CX⁴—(CF₂)_(q)—X⁵wherein X⁴ and X⁵ are H or F, q is an integer of from 1 to 10, andCH₂═C(CF₃)₂. Also one or more monomers copolymerizable therewith, forexample, ethylene, propylene, vinyl chloride, vinyl ethers, carboxylicacid vinyl esters and acryls can be used as copolymerizable components.

Among them, from the viewpoint of chemical resistance and heatresistance, preferable examples of the monomer which is used as a maincomponent are, for instance, a sole use of fluorine-containing olefin, acombination use of fluorine-containing olefins, a combination use ofethylene and TFE and a combination use of ethylene and CTFE.Particularly a sole use of perhalo olefin and a combination use ofperhalo olefins are preferable.

Examples thereof are

-   (1) VdF/TFE (0 to 100/100 to 0), particularly VdF/TFE (70 to 99/30    to 1), PTFE or PVdF;-   (2) ethylene/TFE/HFP (6 to 60/40 to 81/1 to 30),    3,3,3-trifluoropropylene-1,2-trifluoromethyl-3,3,3-trifluoropropylene-1/PAVE    (40 to 60/60 to 40);-   (3) TFE/CF₂═CF-R_(f) ³ (amount exhibiting non-elastomeric property,    namely, an amount of CF₂═CF—R_(f) ³ is not more than 15% by mole.    R_(f) ³ is a linear or branched fluoro or perfluoro alkyl group or    fluoro or perfluoro oxyalkyl group which may have at least one ether    type oxygen atom);-   (4) VdF/TFE/CTFE (50 to 99/30 to 0/20 to 1);-   (5) VdF/TFE/HFP (60 to 99/30 to 0/10 to 1);-   (6) ethylene/TFE (30 to 60/70 to 40);-   (7) polychlorotrifluoroethylene (PCTFE);-   (8) ethylene/CTFE (30 to 60/70 to 40); and the like. Figures in the    parentheses represent % by mole. Among them, from the viewpoint of    chemical resistance and heat resistance, non-elastomeric copolymers,    particularly PTFE and TFE/CF₂═CF—R_(f) ³ (R_(f) ³ is as defined    above) are preferable.

Also the above-mentioned unit Y² giving curing sites may be introducedfor various crosslinking systems as a monomer capable of constitutingthe non-elastomeric segment B in an amount of not more than 5% by mole,preferably not more than 2% by mole.

A block copolymerization of the non-elastomeric segment B can be carriedout, for example, by changing to the monomer for the non-elastomericsegment B subsequently to emulsion polymerization of the elastomericsegment A.

The number average molecular weight of the non-elastomeric segment B canbe adjusted in the wide range of from 1,000 to 1,200,000, preferablyfrom 3,000 to 400,000.

The non-elastomeric segment B can be surely block-copolymerized with theelastomeric segment A when the elastomeric segment A comprises not lessthan 90% by mole, particularly not less than 95% by mole of perhaloolefin unit as a component unit thereof. And also the molecular weight(degree of polymerization) of the non-elastomeric segment B can beincreased.

As mentioned above, X¹ and X² which are the end groups of the elastomerare carboxyl group, alkoxycarbonyl group, iodine atom, bromine atom orsulfonic acid group. Example of the method for introducing such afunctional group to the ends of the elastomer is a method of treatingwith an acid which is described hereinafter.

In the present invention, as mentioned above, fluorine-containingelastomers in which at least one of X¹, X², Y, Y¹ and Y² capable ofbecoming a curing site is a nitrile group, carboxyl group oralkoxycarbonyl group are used preferably. Among them, theabove-mentioned fluorine-containing elastomer having carboxyl group atan end of a trunk chain thereof (namely, at least one of X¹ and X² iscarboxyl group) is a novel elastomer.

The fluorine-containing elastomers (V) and (VI) are characterized inthat they are not polymerization products but fluorine-containingelastomers isolated from a polymerization reaction mixture. Thereforethose elastomers are in the state of so-called mass and can becrosslinked by adding a crosslinking agent or by irradiation of highenergy rays.

So the fluorine-containing elastomers represented by the above-mentionedformulae (V) and (VI) have not been present in the crosslinkable state.

From the viewpoint of securing curing sites to enhance heat resistanceand not to lower mechanical properties such as compression set at hightemperatures, it is preferable that the content of carboxyl group in thefluorine-containing elastomers of the present invention represented bythe formulae (V) and (VI) satisfies the following equation (1).(Sco/Scf)×(D/Dp)×(F/Fp)≧0.01

Then the abbreviations in the equation (1) are explained below.

Sco, Scf, D, Dp, F and Fp in the equation represent the followingrespective values of the aimed fluorine-containing elastomer and astandard perfluoro elastomer mentioned below. Sco: Total area ofabsorbances at the absorptions derived from carbonyl group of associatedand non-associated carboxyl groups having the absorption peaks at from1,680 to 1,830 cm⁻¹ when measurement is made with FT-IR with respect tothe elastomer to be measured. For example, in case ofTFE/perfluoro(methyl vinyl ether) (PMVE)/CF₂═CFOCF₂CF(CF₃)OCF₂CF₂X, inwhich X is CN or COOH, an absorption derived from the associatedcarbonyl group appears at 1,800 to 1,820 cm⁻¹ and an absorption derivedfrom the non-associated carbonyl group appears at 1,760 to 1,780 cm⁻¹.

-   Scf: Area of absorbance at absorption derived from a harmonic sound    of C—F bond having an absorption peak at from 2,220 to 2,840 cm⁻¹    when measurement is made with FT-IR with respect to the elastomer to    be measured. In case where nitrile group is present, Scf is a value    obtained by subtracting an area of absorbance at absorption derived    from nitrile group having an absorption peak at from 2,220 to 2,300    cm⁻¹ from a total area of absorbance at whole absorption having a    peak at from 2,220 to 2,840 cm⁻¹. This correction is made to    eliminate an influence of absorption derived from nitrile group    since a peak of the absorption appears at from 2,220 to 2,300 cm⁻¹    when nitrile group is present.-   D: Specific gravity at 20° C. of the elastomer to be measured.-   Dp: Specific gravity (measured value: 2.03) at 20° C. of a standard    perfluoro elastomer (copolymer of TFE/PMVE in a mole ratio of 58/42,    measured with ¹⁹F-NMR). The reason why the copolymer comprising    TFE/PMVE in a mole ratio of 58/42 is used as a standard perfluoro    elastomer is that it is easily obtainable.-   F: Fluorine content (% by weight) of the elastomer to be measured    which is obtained by elemental analysis.-   Fp: Fluorine content (measured value: 71.6% by weight) of the    above-mentioned standard perfluoro elastomer which is obtained by    elemental analysis.

Then explained below is a meaning which the equation (1) has.

The term Sco/Scf is a proportion of carbonyl group (carbonyl group ofcarboxyl group, hereinafter the same) to C—F bond in the perfluoroelastomer. In case where the fluorine-containing elastomer of thepresent invention is a perfluoro elastomer, only this term may be used.Namely, Sco/Scfp≧0.01 (Scfp: Area absorbance of C—F bond of theperfluoro elastomer).

The terms D/Dp and F/Fp are those used for correction in case where thefluorine-containing elastomer (VI) has a non-perfluoro elastomer, forexample, vinylidene fluoride. Namely, when the non-perfluoro monomersuch as vinylidene fluoride is copolymerized, an amount of C—F bonds inthe elastomer decreases and an area of absorbance of C—F bonds measuredwith a transmission IR analyzer decreases.

In general in case where the measurement is made with a transmission IR,an area absorbance of C—F is proportional to the number of moles offluorine atoms per a unit area of the elastomer (a value obtained bydividing a weight of fluorine atom by an atomic weight 19 of fluorine).Thereby a weight of perfluoro elastomer having a volume V is V×Dp (Dp isa specific gravity of perfluoro elastomer), and thus a weight offluorine in the perfluoro elastomer is V×Dp×Fp/100 (Fp is a fluorinecontent of the perfluoro elastomer (Fp % by weight)) and the number ofmoles of fluorine is V×Dp×Fp/1900. Similarly the number of moles offluorine in a non-perfluoro elastomer having a volume V is V×D×F/1900 (Dand F are a specific gravity and fluorine content of the non-perfluoroelastomer, respectively).

Provided that an area of absorbance of C—F bond of the perfluoroelastomer is Scfp and an area of absorbance of C—F bond of thenon-perfluoro elastomer is Scf, since the area of absorbance of C—F bondis proportional to the number of moles, an equation Scfp/Scf=VDpFp/VDFis obtained and thus an equation Scfp=(DpFp/DF)×Scf is obtained. Whenthis equation is substituted for the equation Sco/Scfp ≧0.01 of theperfluoro elastomer, the above-mentioned equation (1) can be obtained.

In the equation (1), the following measuring methods and apparatuses areused.

(FT-IR Measurement)

Measuring apparatus: FT-IR Spectro Meter Model 1760X available fromPerkin Elmer Co., Ltd.

-   -   Sample: About 0.1 mm thick film    -   Measuring conditions: Resolution 2 cm⁻¹, Detecting interval 1        cm⁻¹, measured by transmission method.        (Elemental Analysis)    -   Measuring apparatus: Micro Processor Ionalyzer Model 901        available from Orion Research Co., Ltd.    -   Measuring method: A small amount of Na₂O₂ (combustion improver)        is added to 1.4 to 1.9 mg of the sample, followed by combustion        in a combustion flask containing 25 ml of pure water. After        allowing to stand for 30 minutes, 10 ml is sampled and thereto        is added 10 ml of a solution (10 liter of a solution comprising        500 ml of acetic acid, 500 g of sodium chloride, 5 g of        tri-sodium citrate dihydrate, 320 g of sodium hydroxide and pure        water). Then an amount of F ion is measured with F ion meter.        (Specific Gravity)    -   Measuring apparatus: Automatic densitometer Model D-1 available        from Kabushiki Kaisha Toyo Seiki Seisakusho    -   Measuring condition: 20° C.

The equation (1) means that the fluorine-containing elastomer,irrespective of perfluoro elastomer or non-perfluoro elastomer, containsnot less than 1 mmol of carboxyl group per 1 kg of the polymer.Particularly preferred is the fluorine-containing elastomer containingfrom 10 to 250 mmol of carboxyl group. When the elastomer is prepared bycopolymerizing a carboxyl group-containing monomer, it is preferablethat a copolymerized proportion of the carboxyl group-containing monomeris from 0.3 to 2% by mole. When other crosslinkable functional groups(for example, nitrile group, etc.) are contained, a total amount ofthose functional groups and carboxyl groups is preferably within theabove-mentioned range.

From the viewpoint of enhancement of physical properties of the obtainedcrosslinked product, carboxyl groups are preferably bonded to the endgroups X¹ and X² of the trunk chain.

The above-mentioned fluorine-containing elastomer can be prepared bypolymerization methods such as emulsion polymerization, suspensionpolymerization and solution polymerization.

It is preferable to use a polymerization initiator which makes itpossible that carboxyl groups or groups capable of forming carboxylgroup (for example, acid fluoride, acid chloride and CF₂OH, any of whichform carboxyl group in the presence of water) are present at an end ofthe elastomer. Examples thereof are ammonium persulfate (APS), potassiumpersulfate (KPS), and the like.

Also a chain transfer agent which is usually used for adjusting amolecular weight may be used. However it is better not to use the chaintransfer agent as far as possible because a proportion of the groupscapable of forming carboxyl groups or alkoxycarbonyl groups to beintroduced into the ends of the elastomer is reduced. In the case wherethe polymerization initiator can make it possible that theabove-mentioned groups are present at the ends of elastomer, however,such a polymerization initiator may be used. When the chain transferagent is not used, the molecular weight of the elastomer may be adjustedby carrying out the polymerization at a low pressure, for example, at apressure less than 2 MPa·G, preferably at a pressure of not more than 1MPa·G. Other polymerization conditions are not limited particularly.However when producing a polymerization product having carboxyl group atan end and/or a branched chain thereof without acid treatment explainedbelow, it is preferable that a pH value of the polymerization system isadjusted to a strong acid having a pH value of not more than 3.

Among the so-obtained polymerization products, some of them do notcontain free carboxyl group depending on the polymerization conditions.However by the acid treatment mentioned below, conversion to freecarboxyl group can be carried out.

In the present invention it is preferable to carry out an acid treatmentof a polymerization product to convert groups such as a metal salt andammonium salt of carboxylic acid present therein to carboxyl group.Examples of the proper acid treatment method are a method of washing thepolymerization product, for example, with hydrochloric acid, sulfuricacid, nitric acid, or the like and a method of adjusting a system of amixture after the polymerization reaction to a pH value of not more than3 with such an acid.

It is preferable from the viewpoint of reduction of steps that the acidtreatment is applied as means for coagulation when isolating thepolymerization product from the polymerization reaction mixture bycoagulation. The polymerization product may be isolated by means offreeze drying, or the like after the acid treatment of thepolymerization mixture. Further a coagulation method by ultrasonic waveor by mechanical force may be employed.

Also carboxyl group can be introduced by oxidizing a fluorine-containingelastomer containing iodine or bromine with a fuming nitric acid.

An amount of the compound (A) which is a crosslinking agent ispreferably from 0.1 to 10 parts by weight based on 100 parts by weightof the elastomer.

To the composition of the present invention can be added additives whichare usually added to a crosslinkable elastomer composition as the casedemands, for example, a filler, processing aid, plasticizer, coloringagent, and the like. In addition to the above-mentioned additives, oneor more of usual crosslinking agent and crosslinking accelerator otherthan the above-mentioned ones may be blended. Also two or moreelastomers may be mixed in a range not lowering an effect of the presentinvention.

The composition of the present invention can be prepared by mixing eachof the above-mentioned components by using usual processing equipmentfor rubber, for example, an open roll, Banbury mixer, kneader, or thelike. In addition, the composition can be prepared also by a method ofusing a closed mixer and a method of co-coagulation through emulsionmixing.

For producing a pre-molded article from the above-mentioned composition,usual known methods may be employed, such as a method of heating andcompressing in a metal mold, a method of putting in a heated metal moldunder pressure and a method of extruding with an extruder. In cases ofextruded products such as a hose and cable, since shapes thereof can bemaintained even after the extruding, a pre-molded article extrudedwithout using a crosslinking agent can be used as it is. Of course, itis possible to use a pre-molded article subjected to crosslinking byheating with steam by using a crosslinking agent. Also in case of ashaped product such as O-ring, when it is difficult to hold a shape ofthe product in an un-crosslinked state after mold-releasing, it ispossible to maintain the shape by using a pre-molded article crosslinkedpreviously by using a crosslinking agent.

A crosslinked product having good physical properties can be obtained ata relatively low crosslinking temperature (for example, from 150° to230° C., preferably from 170° to 200° C.).

The present invention also relates to the so-obtained crosslinkedproduct. In the crosslinked product of the present invention, a highheat resistance which cannot be obtained by conventional imidazolecrosslinking and further excellent mechanical strength and chemicalresistance can be provided. Furthermore a variation per a given periodof time of a compression set at high temperatures which is an index forevaluating a sealing property essential particularly for a sealingmaterial is reduced.

The crosslinked product of the present invention is useful as variousmolded articles in the fields shown in Tables 1, 2 and 3 on thefollowing pages.

TABLE 1 Field of industry Sub-field of industry Final product EquipmentParts Electrical Semi-conductor Semi-conductor CVD equipment O (square)ring, packing, sealing material, tube, roll production apparatuses Dryetching equipment Coating, lining, gasket, diaphragm, hose Liquidcrystal panel Wet etching equipment production apparatus Oxidation anddiffusion Plasma panel production equipment apparatus Sputteringequipment Ashing equipment Cleaning equipment Ion implantation equipmentTransportation Vehicle Car Engine and auxiliary Gasket, shaft seal,valve stem seal, sealing material, hose devices AT devices Hose, sealingmaterial Fuel line and auxiliary O (square) ring, tube, packing, corematerial of valve, devices hose, sealing material, diaphragm AircraftAircraft Fuel line Diaphragm, O (square) ring, valve, tube, packing,hose, sealing material Rocket Rocket Fuel line, engine and Diaphragm, O(square) ring, valve, tube, packing, hose, auxiliary devices sealingmaterial Ship Ship Fuel line Diaphragm, O (square) ring, valve, tube,packing, hose, sealing material Chemical Chemical products PlantProduction line of Lining, valve, packing, roll, hose, diaphragm,chemicals such as O (square) ring, tube, sealing materialpharmaceutical, agricultural chemical, coating and resin (Petroleum)Chemicals Pharmaceuticals Plug for chemicals Plug for chemicalsMechanical Photograph Developing machine Film developing machine RollX-ray film developing Roll machine Printing Printing machine Printingroll Roll Coating Coating facilities Coating roll Roll Analyzer and Tubephysical and chemical appliances Food Plant Food processing line Lining,valve, packing, roll, hose, diaphragm, O (square) ring, tube, sealingmaterial Metal Steel making Steel sheet Steel sheet processing roll Rollprocessing facilities

TABLE 2 Field of Industry Characteristics Required Electrical Plasmaresistance, acid resistance, alkali resistance, amine resistance, ozoneresistance, gas resistance, chemical resistance, cleanliness, heatresistance Transportation Heat resistance, amine resistance Heatresistance, amine resistance Fuel resistance, fuel permeability, heatresistance Fuel resistance, fuel permeability, heat resistance Fuelresistance, fuel permeability, heat resistance Fuel resistance, fuelpermeability, heat resistance Chemical Chemical resistance, solventresistance, heat resistance, steam resistance Chemical resistance,solvent resistance, heat resistance Cleanliness Mechanical Chemicalresistance Chemical resistance Solvent resistance Solvent resistanceFood Chemical resistance, solvent resistance, heat resistance Metal Heatresistance, acid resistance

TABLE 3 Field of industry Parts Electrical O ring and sealing materialfor gate valve of corresponding production equipment O ring and sealingmaterial for quartz window of corresponding production equipment O ringand sealing material for chamber of corresponding production equipment Oring and sealing material for gate of corresponding production equipmentO ring and sealing material for bell jar of corresponding productionequipment O ring and sealing material for coupling of correspondingproduction equipment O ring and sealing material for pump ofcorresponding production equipment O ring and sealing material for gascontroller for semi-conductor of corresponding production equipment Oring and sealing material for resist developing and releasing solutionsO ring and sealing material for wafer cleaning solution Diaphragm ofpump for corresponding production equipment Hose for resist developingand releasing solutions Hose and tube for wafer cleaning solution Rollfor transferring wafer Lining and coating of tanks for resist developingand releasing solutions Lining and coating of tanks for wafer cleaningsolution Lining and coating of tanks for wt etching TransportationEngine head gasket Metal gasket Crank shaft seal Cam shaft seal Valvestem seal Manifold packing Oil hose Seal for oxygen sensor ATF hoseInjector O ring Injector packing O ring and diaphragm for fuel pump Fuelhose Chemical Sealing material for oil well excavator MechanicalDeveloping roll Developing roll Gravure roll Guide roll Gravure roll formagnetic tape production and coating line Guide roll for magnetic tapeproduction and coating line Various coating rolls Food Metal

Particularly the crosslinked product of the present invention can beused built-in the following semiconductor manufacturing equipment.

-   (1) Etching system    -   Dry etching equipment        -   Plasma etching machine        -   Reactive ion etching machine        -   Reactive ion beam etching machine        -   Sputter etching machine        -   Ion beam etching machine    -   Wet etching equipment    -   Ashing equipment-   (2) Cleaning system    -   Dry etching cleaning equipment        -   UV/O₃ cleaning machine        -   Ion beam cleaning machine        -   Laser beam cleaning machine        -   Plasma cleaning machine        -   Gas etching cleaning machine    -   Extractive cleaning equipment        -   Soxhlet extractive cleaning machine        -   High temperature high pressure extractive cleaning machine        -   Microwave extractive cleaning machine        -   Supercritical extractive cleaning machine-   (3) Exposing system    -   Stepper    -   Coater and developer-   (4) Polishing system    -   CMP equipment-   (5) Film forming system    -   CVD equipment    -   Sputtering equipment-   (6) Diffusion and ion implantation system    -   Oxidation and diffusion equipment    -   Ion implantation equipment.

The crosslinked rubber molded article of the present invention issuitable as a sealing material used under temperature environment of notless than 300° C., particularly a sealing material for O₂ sensor ofmotor engine, a sealing material for airplane and space ship engines, asealing material for oil well excavator, etc.

The present invention is then explained by means of examples, but is notlimited to them.

PREPARATION EXAMPLE 1

(Synthesis of Cn Group-Containing Elastomer A)

A 3-liter stainless steel autoclave having no ignition source wascharged with 1 liter of pure water, 10 g of:

as an emulsifying agent and 0.09 g of disodium phosphate 12H₂O as a pHcontrol agent. After the inside of a system was sufficiently replacedwith nitrogen gas and deairing was carried out, the autoclave was heatedto 50° C. with stirring at 600 rpm, and a gas mixture oftetrafluoroethylene (TFE)/perfluoro(methyl vinyl ether) (PMVE)(TFE/PMVE=25/75 in mole ratio) was introduced so that the insidepressure became 0.78 MPa·G. Then 10 ml of an aqueous solution ofammonium persulfate (APS) having a concentration of 527 mg/ml wasintroduced with pressurized nitrogen gas to initiate a reaction.

With the advance of the polymerization, at the time when the insidepressure was lowered to 0.69 MPa·G, 3 g ofCF₂═CFOCF₂CF(CF₃)OCF₂CF₂CN(CNVE) was introduced with pressurizednitrogen. Then 4.7 g of TFE and 5.3 g of PMVE were introduced at therespective self-pressures so that the inside pressure became 0.78 MPa·G.Thereafter with the advance of the reaction, pressurized TFE and PMVEwere introduced similarly. Thus increasing and decreasing of the insidepressure were repeated between 0.69 MPa·G and 0.78 MPa·G, and inaddition, 3 g of CNVE was introduced with pressurized nitrogen at thetime when a total amount of the introduced TFE and PMVE reached 70 g,130 g, 190 g and 250 g, respectively.

Nineteen hours after starting of the polymerization, when a total amountof the introduced TFE and PMVE reached 300 g, the autoclave was cooledand an un-reacted monomer was released to obtain 1,330 g of an aqueousdispersion having a solid concentration of 21.2% by weight.

Then 1,196 g of the obtained aqueous dispersion was diluted with 3,588 gof water and added slowly to 2,800 g of an aqueous solution of 3.5% byweight of hydrochloric acid with stirring. After the addition, stirringwas continued for five minutes and then a coagulated product wasfiltrated. The obtained polymer was put in 2 kg of HCFC-141b, followedby stirring for five minutes and filtrating again. After that, thewashing with HCFC-141b and the filtration were repeated four times andvacuum drying was carried out at 60C for 72 hours to obtain 240 g of apolymer (nitrile group-containing elastomer A).

As a result of ¹⁹F-NMR analysis, the obtained polymer was a polymercomprising TFE/PMVE/CNVE=56.6/42.3/1.1% by mole. Also as a result ofmeasurement by infrared spectroscopic analysis, a chart shown in FIG. 1was obtained.

In the chart of FIG. 1, a characteristic absorption of carboxyl groupwas recognized around 1,774.9 cm⁻¹ and 1,808.6 cm⁻¹ and a characteristicabsorption of OH group was recognized around 3,557.5 cm⁻¹ and 3,095.2cm⁻¹.

When an elastomer obtained by coagulation of the obtained product withmagnesium chloride and ethanol was subjected to IR analysis forreference purpose, an absorption derived from carboxyl group was notpresent and an absorption of magnesium salt of carboxylic acid wasrecognized at 1,729 cm⁻¹.

Further when the coagulation was carried out by freeze coagulation (pH:3.5 to 7.0) and the obtained elastomer was subjected to IR analysissimilarly, an absorption derived from carboxyl group was not present andan absorption of ammonium salt (—COONH₄) of carboxylic acid wasrecognized at 1,651 cm⁻¹.

A value obtained from the equation (Sco/Scf)×(D/Dp)×(F/Fp) was 0.040.

PREPARATION EXAMPLE 2

(Synthesis of COOH Group-Containing Elastomer)

A 3-liter stainless steel autoclave having no ignition source wascharged with 1 liter of pure water, 10 g of:

as an emulsifying agent and 0.09 g of disodium phosphate-12H₂O as a pHcontrol agent. After the inside of a system was sufficiently replacedwith nitrogen gas and deairing was carried out, the autoclave was heatedto 50° C. with stirring at 600 rpm, and a gas mixture oftetrafluoroethylene (TFE)/perfluoro(methyl vinyl ether) (PMVE)(TFE/PMVE=25/75 in mole ratio) was introduced so that the insidepressure became 0.78 MPa·G. Then 10 ml of an aqueous solution ofammonium persulfate (APS) having a concentration of 527 mg/ml was isintroduced with pressurized nitrogen gas to initiate a reaction.

With the advance of the polymerization, at the time when the insidepressure was lowered to 0.69 MPa·G, 1.89 g ofCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOH (CBVE) was introduced with pressurizednitrogen. Then 4.7 g of TFE and 5.3 g of PMVE were introduced at therespective self-pressures so that the inside pressure became 0.78 MPa·G.Thereafter with the advance of the reaction, pressurized TFE and PMVEwere introduced similarly. Thus increasing and decreasing of the insidepressure were repeated between 0.69 MPa·G and 0.78 MPa·G. 4.2 hoursafter starting of the polymerization reaction, when a total amount ofthe introduced TFE and PMVE reached 80 g, the autoclave was cooled andan un-reacted monomer was released to obtain 1,089 g of an aqueousdispersion having a solid concentration of 7.5% by weight.

Then 1,000 g of the obtained aqueous dispersion was diluted with 3,000 gof water and added slowly to 2,800 g of an aqueous solution of 3.5% byweight of hydrochloric acid with stirring. After the addition, stirringwas continued for five minutes and then a coagulated product wasfiltrated. The obtained polymer was put in 800 g of HCFC-141b, followedby stirring for five minutes and filtrating again. After that, thewashing with HCFC-141b and the filtration were repeated four times andvacuum drying was carried out at 120° C. for 72 hours to obtain 70 g ofa polymer.

As a result of ¹⁹F-NMR analysis, the obtained polymer was a polymercomprising TFE/PMVE/CBVE=59.6/39.9/0.5% by mole. Also as a result ofmeasurement by infrared spectroscopic analysis, a characteristicabsorption of carboxyl group was recognized around 1,774.4 cm⁻¹ and acharacteristic absorption of OH group was recognized around 3,557.0 cm⁻¹and 3,087.7 cm⁻¹.

A value obtained from the equation (Sco/Scf)×(D/Dp)×(F/Fp) was 0.21.

PREPARATION EXAMPLE 3

(Synthesis of CN Group-Containing Elastomer B)

A 45-liter stainless steel autoclave having no ignition source wascharged with 27 liter of pure water, 270 g of:

as an emulsifying agent and 2.4 g of disodium phosphate-12H₂O as a pHcontrol agent. After the inside of a system was sufficiently replacedwith nitrogen gas and deairing was carried out, the autoclave was heatedto 50° C. with stirring at 200 rpm, and a gas mixture oftetrafluoroethylene (TFE)/perfluoro(methyl vinyl ether) (PMVE)(TFE/PMVE=25/75 in mole ratio) was introduced so that the insidepressure became 0.78 MPa·G. Then 473 ml of an aqueous solution ofammonium persulfate (APS) having a concentration of 0.3 g/ml wasintroduced with pressurized nitrogen gas to initiate a reaction.

With the advance of the polymerization, at the time when the insidepressure was lowered to 0.69 MPa·G, 15.3 g ofCF₂═CFOCF₂CF(CF₃)OCF₂CF₂CN(CNVE) was introduced with pressurizednitrogen. Then 54 g of TFE and 60 g of PMVE were introduced at therespective self-pressures so that the inside pressure became 0.78 MPa·G.Thereafter with the advance of the reaction, pressurized TFE and PMVEwere introduced similarly. Thus increasing and decreasing of the insidepressure were repeated between 0.69 MPa·G and 0.78 MPa·G. When a totalamount of the introduced TFE and PMVE reached 550 g and 980 g,respectively and thereafter every time when the total amount increasedby 430 g, 15.3 g of CNVE was introduced with pressurized nitrogen gas.

9.4 hours after starting of the polymerization, when the total amount ofthe introduced TFE and PMVE reached 7,000 g, the autoclave was cooledand an un-reacted monomer was released to obtain 34.8 kg of an aqueousdispersion having a solid concentration of 20.6% by weight.

The obtained aqueous dispersion was subjected to coagulating withhydrochloric acid and drying in the same manner as in PreparationExample 1 to obtain a polymer (nitrile group-containing elastomer B).

As a result of ¹⁹F-NMR analysis, the obtained polymer was a polymercomprising TFE/PMVE/CNVE=61.7/37.5/0.8% by mole.

PREPARATION EXAMPLE 4

(Synthesis of 2,2-bis[3-amino-4-(N-methylamino)phenyl]hexafluoropropane(AFTA-Me))

All the following reactions were carried out under nitrogen gasatmosphere, and all the reagents and solvents were those dehydrated.

In 50 ml of dichloromethane were dissolved 4.963 g (26.03 mmol) ofp-toluenesulfonyl chloride and 4.623 g (10.85 mmol) of2,2-bis(3-nitro-4-hydroxyphenyl)hexafluoropropane [Amino(bisphenol)AF].The solution was cooled to 0° C. and 6.05 ml of triethylamine was addeddropwise into the solution. After the addition, stirring was continuedat 0° C., and one hour later, the solution temperature was restored toroom temperature and the solution was stirred for three hours.

With the advance of the reaction, crystals were precipitated. To thereaction solution was added 30 ml of dilute hydrochloric acid, and thecrystals were collected by filtration. After the filtrated product waswashed with water and then with a 50% aqueous solution of methanol,re-crystallization (hexane/THF) was carried out to obtain 6.3 g (yield:80%) of 2,2-bis-(3-nitro-4-tosyloxyphenyl)hexafluoropropane aslight-yellow crystals.

3 g (4.08 mmol) of 2,2-bis-(3-nitro-4-tosyloxyphenyl)hexafluoropropanewas dissolved in 70 ml of butyl acetate, followed by moderately heatingand refluxing. Then 5.26 ml (40.8 mmol) of n-methylbenzylamine was addeddropwise into the solution, and after heating and refluxing werecontinued for 12 hours, the solution was cooled to room temperature.After 20 ml of dilute hydrochloric acid was added and extraction withethyl acetate was carried out two times, an organic layer was washedwith dilute hydrochloric acid, an aqueous solution of sodiumhydrogencarbonate and saturated brine. After the washed organic layerwas dried with anhydrous magnesium sulfate, the solvent was distilledoff under reduced pressure. The obtained liquid product was separated bysilica gel chromatography (hexane/ethyl acetate=4/1,hexane/dichloromethane=1/1) to obtain 2.1 g (yield: 81%) of2,2-bis-[3-nitro-4(N-methyl-N-benzylamino)phenyl]hexafluoropropane inthe form of yellow solid.

Then 10 g (15.8 mmol) of the obtained2,2-bis-[3-nitro-4(N-methyl-N-benzylamino)phenyl]hexafluoropropane wasdissolved in 150 ml of methanol and thereto was added 500 mg of 20%palladium hydroxide on carbon, and then replaced by hydrogen, followedby stirring vigorously at room temperature under hydrogen atmosphere for48 hours. After the reaction solution was filtrated with Celite tofiltrate off the catalyst, methanol was distilled off.

The obtained liquid product was separated by silica gel columnchromatography (hexane/ethyl acetate=4/1) to obtain a crude product.This product was dissolved in 50 ml of diethylether and thereto wasgradually added 1N hydrochloric acid-diethylether solution. Theprecipitated hydrochloric acid salt was filtrated, washed withdiethylether and then dissolved in 100 ml of water. Thereto was addeddropwise 14% aqueous ammonia under nitrogen atmosphere until a pH valuebecame 7. A precipitate was filtrated, washed with deaerated waterstrongly and then dried at 35° C. under reduced pressure until a weightbecame constant to obtain 4.5 g (yield: 72%) of2,2-bis[3-amino-4-(N-methylamino)phenyl]hexafluoropropane in the form ofwhite solid.

The following physical properties of the obtained product weredetermined.

-   Melting point: 67.1° to 70.2° C. (purity: 94%)    -   ¹H-NMR (in CDCl₃): δ(ppm)=6.57 to 6.98 (6H, m, aromatic ring),        2.80 to 3.40 (4H, broad, NH₂), 2.838 (6H, s, CH₃)    -   ¹⁹F-NMR (in CDCl₃): δ(ppm)=−64.8 (s, CF₃)    -   IR (KBr): cm⁻¹=3,337 to 3,147 (broad, strong, NH₂, NH), 1,270 to        1,140 (broad, strong, CF₃)    -   MS m/z=392 (m+), 291-   HRMS: C₁₇H₁₈F₆N₄ (m+)    -   Calculated value=392.144    -   Measured value: 392.145.

EXAMPLE 1

The fluorine-containing elastomer having nitrile group and carboxylgroups at ends thereof which was obtained in Preparation Example 1,2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane (AFTA-Ph)which is a crosslinking agent synthesized by the above-mentioned processdescribed in Journal of Polymer Science, edited by Polymer Chemistry,Vol. 20, pp. 2381 to 2393 (1982), and carbon black (Thermax N-990available from Cancarb Co., Ltd.) as a filler were mixed in a weightratio of 100/2.83/20, and the mixture was kneaded with an open roll toobtain a crosslinkable fluorine-containing rubber composition.

After the fluorine-containing rubber composition was subjected tocrosslinking by pressing at 180° C. for 10 minutes, further a two-stagedcrosslinking in an oven was carried out at 204° C. for 18 hours and thenat 288° C. for 18 hours. Thus a 2 mm thick crosslinked product and asample O-ring (AS-568A-214) were produced. The results of measurementssuch as crosslinkability, physical properties in normal state, heatresistance and compression set of the crosslinked product are shown inTable 4.

(Crosslinkability)

Vulcanization curves of each composition for crosslinking are obtainedat a temperature shown in Table 4 with JSR Curastometer Model II andthen a minimum viscosity (v min), maximum viscosity (v max), inductiontime (T₁₀) and optimum vulcanization time (T₉₀) are obtained.

(Physical Properties in Normal State)

A 100% modulus, tensile strength, elongation and hardness (IRHD) of a 2mm thick crosslinked product in normal state (25° C.) are measuredaccording to JIS K6301.

(Heat Resistance)

After the crosslinked product is heated at 300° C. for 70 hours, a 100%modulus, tensile strength, elongation and hardness (IRHD) of a 2 mmthick crosslinked product in normal state (25° C.) are measuredaccording to JIS K6301. Further a ratio of variation from the physicalproperties in normal state (variation rate) is calculated.

(Compression Set)

A compression set of the O-ring (AS-568A-214) is measured according toJIS K630I after allowing to stand at 300° C. for 70 hours and at 300° C.for 168 hours, respectively.

EXAMPLE 2

A crosslinkable composition and crosslinked product were produced in thesame manner as in Example 1 except that the fluorine-containingelastomer having COOH group which was prepared in Preparation Example 2was used as an elastomer and the crosslinking by pressing was carriedout at 200° C. for 80 minutes. Physical properties were measured in thesame manner as in Example 1. The results are shown in Table 4.

EXAMPLE 3

A crosslinkable composition and crosslinked product were produced in thesame manner as in Example 2 except that2,2-bis[3-amino-4-(N-methylamino)phenyl]hexafluoropropane obtained inPreparation Example 3 was used as a crosslinking agent, an adding amountof the crosslinking agent was 2.18 parts by weight and the crosslinkingby pressing was carried out at 200° C. for 35 minutes. Physicalproperties were measured in the same manner as in Example 1. The resultsare shown in Table 4.

COMPARATIVE EXAMPLE 1

A crosslinkable composition and crosslinked product were produced in thesame manner as in Example 1 except that2,2-bis(3,4-diaminophenyl)hexafluoropropane (AFTA) was used as acrosslinking agent and an adding amount thereof was 2 parts by weight.Physical properties were measured in the same manner as in Example 1.The results are shown in Table 4.

COMPARATIVE EXAMPLE 2

A crosslinkable composition and crosslinked product were produced in thesame manner as in Example 2 except that2,2-bis(3,4-diaminophenyl)hexafluoropropane (AFTA) was used as acrosslinking agent and an adding amount thereof was 2 parts by weight.Physical properties were measured in the same manner as in Example 2.The results are shown in Table 4.

TABLE 4 Ex. 1 Ex. 2 Ex. 3 Com. Ex. 1 Com. Ex. 2 Components ofcomposition CN-containing elastomer A 100 100 COOH-containing elastomer100 100 100 AFTA-Ph 2.83 2.83 AFTA-Me 2.18 AFTA 2 2 Carbon black 20 2020 20 20 Crosslinkability (200° C.) Minimum viscosity (kgf) 0.24 0.270.21 0.39 0.47 (N)  (2.35 N)  (2.65 N)  (2.06 N)  (3.82 N)  (4.61 N)Maximum viscosity (kgf) 3.21 1.90 1.31 4.42 2.82 (N) (31.46 N) (18.62 N)(12.84 N) (43.32 N) (27.64 N) Induction time (min) 2.5 3.0 3.4 1.0 1.9Optimum vulcanization time (min) 6.2 78.8 33.5 3.7 27.0 Physicalproperties in normal state 100% modulus (MPa) 10.4 7.9 7.9 17.8 7.6Tensile strength (MPa) 19.2 16.7 17.5 20.9 20.2 Elongation (%) 149 174186 107 195 Hardness (IRHD) 68 68 67 76 68 Heat resistance (300° C. × 70hours) 100% modulus (MPa) 12.3 7.7 — 14.0 5.6 Variation rate (%)(+18.9%) (−3.2%) (—) (−21.4%) (−27.2%) Tensile strength (MPa) 19.0 19.7— 18.2 12.6 Variation rate (%) (−1.0%) (+18.2%) (—) (−12.7%) (−37.4%)Elongation (%) 129 174 — 119 228 Variation rate (%) (−13.4%) (+1.1%) (—)(+11.2%) (+16.9%) Hardness (IRHD) 67 68 — 72 66 Compression set 300° C.× 70 hours (%) — 42 — — 44 300° C. × 168 hours (%) — 45 — — 60 -: Notmeasured

As shown in Table 4, the crosslinked product having excellent heatresistance can be obtained when the crosslinking agent of the presentinvention is used.

EXAMPLES 4 to 6

A crosslinkable composition and crosslinked product were produced in thesame manner as in Example 1 except that the CN-containing elastomer Bobtained in Preparation Example 3 was used as a CN-containing elastomer,carbon black (Thermax N-990 available from Cancarb Co., Ltd., Example4), SiO₂ (CABOCYL M-7D available from Cabot Co., Ltd., Example 5) andTiO₂ (TM-1 available from Fuji Titanium Kogyo Kabushiki Kaisha, Example6) were used as a filler, and adding amounts thereof were as shown inTable 5. Physical properties were measured in the same manner as inExample 1. The results are shown in Table 5.

COMPARATIVE EXAMPLE 3

A crosslinkable composition and crosslinked product were produced in thesame manner as in Example 4 except that2,2-bis(3,4-diaminophenyl)hexafluoropropane (AFTA) was used as acrosslinking agent and an adding amount thereof was 2 parts by weight.Physical properties were measured in the same manner as in Example 4.The results are shown in Table 5.

TABLE 5 Com. Ex. 4 Ex. 5 Ex. 6 Ex. 3 Components of compositionCN-containing elastomer B 100 100 100 100 AFTA-Ph 2.83 2.83 2.83 AFAP 2Carbon black 20 20 SiO₂ 10 TiO₂ 30 Crosslinkability (200° C.) Minimumviscosity (kgf) 0.21 0.26 0.20 0.47 Maximum viscosity (kgf) 2.78 2.191.92 2.82 Induction time (min) 2.7 3.5 4.3 1.9 Optimum vulcanizationtime 6.1 10.8 16.9 27.0 (min) Physical properties in normal state 100%modulus (MPa) 7.1 4.8 4.2 7.6 Tensile strength (MPa) 15.8 13.4 13.1 20.2Elongation (%) 157 196 176 195 Hardness (IRHD) 76 77 69 68 Compressionset 300° C. × 70 hours (%) 71 42 32 — 300° C. × 168 hours (%) 88 45 52 —-: Not measured

EXAMPLE 7 and COMPARATIVE EXAMPLE 4

With respect to the crosslinked products produced in Example 4 andComparative Example 3, ethylenediamine resistance and steam resistanceof them were evaluated. The results are shown in Table 6.

(Ethylenediamine Resistance)

A sample was produced from the sheet-like crosslinked product and wasdipped in ethylenediamine at 100° C. for 168 hours to measure variations(%) of volume and weight according to JIS K630 I.

(Steam Resistance)

A 3 mm×2 mm×20 mm crosslinked product was used as a sample. Aftermeasuring the weight and specific weight of the sample, the sample wasput in a 4-ml stainless steel pressure resistant vessel with 1 g ofwater, and the vessel was sealed. After heating the inside of the vesselto 288° C. and allowing to stand for 168 hours, the inside temperatureof the vessel was restored to room temperature. The weight and specificweight of the sample were measured to obtain variations (%) of weightand volume after treating with steam.

TABLE 6 Ethylenediamine resistance Steam resistance (100° C. × 168hours) (288° C. × 168 hours) Variation Variation Variation Variation ofof of of weight volume weight volume (%) (%) (%) (%) Ex. 7 +8 +15 −1.4−1.0 Com. Ex. 4 +51 +109 +8 +69

INDUSTRIAL APPLICABILITY

The present invention can provide a novel crosslinkable elastomercomposition and crosslinking agent from which a crosslinked rubbermolded article having excellent chemical resistance and mechanicalstrength and possessing enhanced heat resistance, particularly heatresistance at high temperatures can be obtained.

1. An elastomer composition for crosslinking which comprises (A) acompound having at least two crosslinkable reactive groups representedby the formula (I):

wherein R¹ in each of the at least two crosslinkable reactive groups isthe same or different and each is fluorine atom or a monovalent organicgroup, and (B) an elastomer having a curing site capable of reactingwith the crosslinkable reactive group (I).
 2. The composition of claim1, wherein the compound (A) is a compound represented by the formula(II):

in which R¹ is as defined above, wherein R² is —SO₂—, —O—, —CO—, analkylene group which may have been substituted,

or a single bond.
 3. The composition of claim 2, wherein in the formula(II), R² is a non-substituted alkylene group having 1 to 6 carbon atomsor a perfluoro alkylene group having 1 to 10 carbon atoms.
 4. Thecomposition of claim 3, wherein in the formula (II), R² is:


5. A crosslinking agent comprising a compound (A) having at least twocrosslinkable reactive groups represented by the formula (I):

wherein R¹ in each of the at least two crosslinkable reactive groups isthe same or different and each is fluorine atom or a monovalent organicgroup.
 6. The crosslinking agent of claim 5, wherein the compound (A) isa compound represented by the formula (II):

in which R¹ is as defined above, wherein R² is —SO₂—, —O—, —CO—, analkylene group which may have been substituted,

or a single bond.
 7. The crosslinking agent of claim 6, wherein in theformula (II), R² is a non-substituted alkylene group having 1 to 6carbon atoms or a perfluoro alkylene group having 1 to 10 carbon atoms.8. The crosslinking agent of claim 7, wherein in the formula (II), R²is:


9. A compound represented by the formula (III):

wherein R³ is an alkyl group which has 1 to 6 carbon atoms and may havebeen substituted.
 10. A crosslinked rubber molded article obtained bycrosslinking the elastomer composition for crosslinking of claim
 1. 11.The composition of claim 1, wherein in the formula (I), the N—R¹ bondhas a higher anti-oxidizing property than the N—H bond.
 12. Thecomposition of claim 1, wherein in the formula (I), R¹ is an aliphatichydrocarbon group which may have been substituted or a benzyl group orphenyl group which may have been substituted.
 13. The composition orclaim 1, wherein in the formula (I), at least one of R¹ is an alkylgroup having 1 to 10 carbon atoms or an alkyl group having fluorine atomand 1 to 10 carbon atoms.
 14. The composition of claim 1, wherein in theformula (I), at least one of R¹ is a phenyl group, a benzyl group, or abenzyl group or phenyl group in which 1 to 5 hydrogen atoms have beensubstituted by fluorine atom or —CF₃.
 15. The composition of claim 1,wherein the elastomer (B) has a nitrile group, carboxyl group and/oralkoxycarbonyl group as a curing site.
 16. The composition of claim 1,wherein the elastomer (B) is a fluorine-containing elastomer.
 17. Thecomposition of claim 16, wherein the fluorine-containing elastomer (B)is a perfluoro elastomer.
 18. The composition of claim 2, wherein in theformula (II), the N—R¹ bond has a higher anti-oxidizing property thanthe N—H bond.
 19. The composition of claim 2, wherein in the formula(II), R¹ is an aliphatic hydrocarbon group which may have beensubstituted or a benzyl group or phenyl group which may have beensubstituted.
 20. The composition of claim 2, wherein in the formula(II), at least one of R¹ is an alkyl group having 1 to 10 carbon atomsor an alkyl group having fluorine atom and 1 to 10 carbon atoms.
 21. Thecomposition of claim 2, wherein in the formula (II), at least one of R¹is a phenyl group, a benzyl group, or a benzyl group or phenyl group inwhich 1 to 5 hydrogen atoms have been substituted by fluorine atom or—CF₃.
 22. The composition of claim 2, wherein the elastomer (B) has anitrile group, carboxyl group and/or alkoxycarbonyl group as a curingsite.
 23. The composition or claim 2, wherein the elastomer (B) is afluorine-containing elastomer.
 24. The composition of claim 23, whereinthe fluorine-containing elastomer (B) is a perfluoro elastomer.
 25. Thecrosslinking agent of claim 5, wherein in the formula (I), R¹ is analiphatic hydrocarbon group which may have been substituted or a benzylgroup or phenyl group which may have been substituted.
 26. Thecrosslinking agent of claim 5, wherein in the formula (I), at least oneof R¹ is an alkyl group having 1 to 10 carbon atoms or an alkyl grouphaving fluorine atom and 1 to 10 carbon atoms.
 27. The crosslinkingagent of claim 5, wherein in formula (I), at least one of R¹ is a phenylgroup, a benzyl group, or a benzyl group or phenyl group in which 1 to 5hydrogen atoms have been substituted by fluorine atom or —CF₃.
 28. Thecrosslinking agent of claim 6, wherein in the formula (II), R¹ is analiphatic hydrocarbon group which may have been substituted or a benzylgroup or phenyl group which may have been substituted.
 29. Thecrosslinking agent of claim 6, wherein in the formula (II), at least oneof R¹ is an alkyl group having 1 to 10 carbon atoms or an alkyl grouphaving fluorine atom and 1 to 10 carbon atoms.
 30. The crosslinkingagent of claim 6, wherein in the formula (II), at least one of R¹ is aphenyl group, a benzyl group, or a benzyl group or phenyl group which 1to 5 hydrogen atoms have been substituted by fluorine atom or —CF₃.